Apparatus for fixing sheet-like materials to a target tissue

ABSTRACT

A device for attaching a sheet-like implant to a target tissue. The device includes a fastener push rod including a first portion, a second portion and a force limiting mechanism operably coupled between the first portion and the second portion. A fastener is carried by the second portion of the fastener push rod. The force limiting mechanism transmits longitudinal movement of the first portion to the second portion while the forces applied to the fastener by the fastener push rod are less than a predetermined value such that longitudinal movement of the first portion of the fastener push rod causes substantially equivalent longitudinal movement of the second portion. The force limiting mechanism allows relative longitudinal motion between the first and second portions while the forces applied to the fastener are equal to or greater than the predetermined value such that the application of undue forces to the fastener is prevented.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 13/397,573, filed on Feb. 15, 2012, now U.S. Pat. No. 9,033,201, which claims priority to U.S. Provisional Application No. 61/443,180 filed on Feb. 15, 2011, the disclosures of each incorporated herein by reference.

FIELD

The present invention relates generally to orthopedic medicine and surgery. More particularly, the present invention relates to methods and apparatus for delivery and fixation of sheet-like materials, such as for treating articulating joints.

BACKGROUND

The glenohumeral joint of the shoulder is found where the head of the humerus mates with a shallow depression in the scapula. This shallow depression is known as the glenoid fossa. Six muscles extend between the humerus and scapula and actuate the glenohumeral joint. These six muscles include the deltoid, the teres major, and the four rotator cuff muscles. As disclosed by Ball et al. in U.S. Patent Publication No. US 2008/0188936 A1 and as illustrated in FIG. 1 the rotator cuff muscles are a complex of four muscles. These four muscles are the supraspinatus, the infraspinatus, the subscapularis, and the teres minor. The centering and stabilizing roles played by the rotator cuff muscles are critical to the proper function of the shoulder. The rotator cuff muscles provide a wide variety of moments to rotate the humerus and to oppose unwanted components of the deltoid and pectoralis muscle forces.

The four muscles of the rotator cuff arise from the scapula 12. The distal tendons of the rotator cuff muscles splay out and interdigitate to form a common continuous insertion on the humerus 14. The subscapularis 16 arises from the anterior aspect of the scapula 12 and attaches over much of the lesser tuberosity of the humerous. The supraspinatus muscle 18 arises from the supraspinatus fossa of the posterior scapula, passes beneath the acromion and the acromioclavicular joint, and attaches to the superior aspect of the greater tuberosity 11. The infraspinatus muscle 13 arises from the infraspinous fossa of the posterior scapula and attaches to the posterolateral aspect of the greater tuberosity 11. The teres minor 15 arises from the lower lateral aspect of the scapula 12 and attaches to the lower aspect of the greater tuberosity 11.

The mechanics of the rotator cuff muscles 10 are complex. The rotator cuff muscles 10 rotate the humerus 14 with respect to the scapula 12, compress the humeral head 17 into the glenoid fossa providing a critical stabilizing mechanism to the shoulder (known as concavity compression), and provide muscular balance. The supraspinatus and infraspinatus provide 45 percent of abduction and 90 percent of external rotation strength. The supraspinatus and deltoid muscles are equally responsible for producing torque about the shoulder joint in the functional planes of motion.

The rotator cuff muscles 10 are critical elements of this shoulder muscle balance equation. The human shoulder has no fixed axis. In a specified position, activation of a muscle creates a unique set of rotational moments. For example, the anterior deltoid can exert moments in forward elevation, internal rotation, and cross-body movement. If forward elevation is to occur without rotation, the cross-body and internal rotation moments of this muscle must be neutralized by other muscles, such as the posterior deltoid and infraspinatus. The timing and magnitude of these balancing muscle effects must be precisely coordinated to avoid unwanted directions of humeral motion. Thus the simplified view of muscles as isolated motors, or as members of force couples must give way to an understanding that all shoulder muscles function together in a precisely coordinated way—opposing muscles canceling out undesired elements leaving only the net torque necessary to produce the desired action. Injury to any of these soft tissues can greatly inhibit ranges and types of motion of the arm.

With its complexity, range of motion and extensive use, a fairly common soft tissue injury is damage to the rotator cuff or rotator cuff tendons. Damage to the rotator cuff is a potentially serious medical condition that may occur during hyperextension, from an acute traumatic tear or from overuse of the joint. With its critical role in abduction, rotational strength and torque production, the most common injury associated with the rotator cuff region is a strain or tear involving the supraspinatus tendon. A tear in the supraspinitus tendon 19 is schematically depicted in FIG. 2. A tear at the insertion site of the tendon with the humerus, may result in the detachment of the tendon from the bone. This detachment may be partial or full, depending upon the severity of the injury. Additionally, the strain or tear can occur within the tendon itself. Injuries to the supraspinatus tendon 19 and recognized modalities for treatment are defined by the type and degree of tear. The first type of tear is a full thickness tear as also depicted in FIG. 2, which as the term indicates is a tear that extends through the thickness of the supraspinatus tendon regardless of whether it is completely tom laterally. The second type of tear is a partial thickness tear which is further classified based on how much of the thickness is tom, whether it is greater or less than 50% of the thickness.

The accepted treatment for a full thickness tear or a partial thickness tear greater than 50% includes reconnecting the tom tendon via sutures. For the partial thickness tears greater than 50%, the tear is completed to a full thickness tear by cutting the tendon prior to reconnection. In contrast to the treatment of a full thickness tear or a partial thickness tear of greater than 50%, the treatment for a partial thickness tear less than 50% usually involves physical cessation from use of the tendon, i.e., rest. Specific exercises can also be prescribed to strengthen and loosen the shoulder area. In many instances, the shoulder does not heal and the partial thickness tear can be the source of chronic pain and stiffness. Further, the pain and stiffness may cause restricted use of the limb which tends to result in further degeneration or atrophy in the shoulder. Surgical intervention may be required for a partial thickness tear of less than 50%, however, current treatment interventions do not include repair of the tendon, rather the surgical procedure is directed to arthroscopic removal of bone to relieve points of impingement or create a larger tunnel between the tendon and bone that is believed to be causing tendon damage. As part of the treatment, degenerated tendon may also be removed using a debridement procedure in which tendon material is ablated. Again, the tendon partial tear is not repaired. Several authors have reported satisfactory early post operative results from these procedures, but over time recurrent symptoms have been noted. In the event of recurrent symptoms, many times a patient will “live with the pain”. This may result in less use of the arm and shoulder which further causes degeneration of the tendon and may lead to more extensive damage. A tendon repair would then need to be done in a later procedure if the prescribed treatment for partial tear was unsuccessful in relieving pain and stiffness or over time the tear propagated through injury or degeneration to a full thickness tear or a partial thickness tear greater than 50% with attendant pain and debilitation. A subsequent later procedure would include the more drastic procedure of completing the tear to full thickness and suturing the ends of the tendon back together. This procedure requires extensive rehabilitation, has relatively high failure rates and subjects the patient who first presented and was treated with a partial thickness tear less than 50% to a second surgical procedure.

As described above, adequate treatments do not currently exist for repairing a partial thickness tear of less than 50% in the supraspinatus tendon. Current procedures attempt to alleviate impingement or make room for movement of the tendon to prevent further damage and relieve discomfort but do not repair or strengthen the tendon. Use of the still damaged tendon can lead to further damage or injury. Prior damage may result in degeneration that requires a second more drastic procedure to repair the tendon. Further, if the prior procedure was only partially successful in relieving pain and discomfort, a response may be to use the shoulder less which leads to degeneration and increased likelihood of further injury along with the need for more drastic surgery. There is a large need for surgical techniques and systems to treat partial thickness tears of less than 50% and prevent future tendon damage by strengthening or repairing the native tendon having the partial thickness tear.

SUMMARY OF THE DISCLOSURE

The disclosure is directed to devices for attaching a sheet-like implant to a target tissue. One embodiment includes a fastener push rod including a first portion, a second portion and a force limiting mechanism operably coupled between the first portion and the second portion. A fastener is carried by the second portion of the fastener push rod. An actuator assembly coupled to the first portion of the fastener push rod is provided. The actuator assembly is capable of creating longitudinal movement of the first portion. The force limiting mechanism transmits longitudinal movement of the first portion to the second portion while the forces applied to the fastener by the fastener push rod are less than a predetermined value such that longitudinal movement of the first portion of the fastener push rod causes substantially equivalent longitudinal movement of the second portion. The force limiting mechanism allows relative longitudinal motion between the first portion and the second portion while the forces applied to the fastener are equal to or greater than the predetermined value such that the application of undue forces to the fastener is prevented.

Another embodiment includes a pronged sheath. The pronged sheath defines a lumen. The pronged sheath includes at least a pair of prongs extending distally beyond a distal end of the lumen such that the prongs form pilot holes when a distal portion of the pronged sheath is pressed against the target tissue. A fastener push rod extends into the lumen defined by the pronged sheath. The fastener push rod includes a first portion, a second portion and a force limiting mechanism operably coupled between the first portion and the second portion. A pair of stakes are disposed at a distal end of the second portion of the fastener push rod. The pair of stakes carries a fastener. An actuator assembly is coupled to the first portion of the fastener push rod and capable of creating longitudinal movement of the first portion of the fastener push rod relative to the pronged sheath. The force limiting mechanism transmits longitudinal movement of the first portion to the second portion while the forces applied to the fastener by the fastener push rod are less than a predetermined value such that longitudinal movement of the first portion of the fastener push rod causes substantially equivalent longitudinal movement of the second portion. The force limiting mechanism allowing relative longitudinal motion between the first portion and the second portion while the forces applied to the fastener are equal to or greater than the predetermined value such that the application of undue forces to the fastener is prevented. In some embodiments, the fastener comprises a staple and each stake has a distal portion and a proximal portion with each distal portion being dimensioned to extend into a passage defined by the staple. Each proximal stake portion has a width larger than a width of each distal portion so that a shoulder of each proximal portion contacts a proximal surface of the staple to apply pushing forces thereto.

In some exemplary embodiments, the force limiting mechanism comprises a constant force spring. A first end of the constant force spring may be coupled to the first portion of the fastener push rod and a second end of the constant force spring may be coupled to the second portion of the fastener push rod.

In some exemplary embodiments, the first portion of the fastener push rod includes a first tubular member, the second portion of the fastener push rod includes a second tubular member, and a portion of one tubular member is slidingly received in a lumen defined by the other tubular member such that the first tubular member and the second tubular member can translate relative to each other. For instance, the first portion of the fastener push rod may include a first tubular member, the second portion of the fastener push rod may include a second tubular member, and a portion of the first tubular member may be slidingly received in a lumen defined by the second tubular member such that the first tubular member and the second tubular member can translate relative to each other. In some exemplary embodiments, the second tubular member defines a slot and the first tubular member carries a pin that is slidingly received in the slot such that relative rotation between the first tubular member and the second tubular member is prevented. The force limiting mechanism may include a constant force spring having a first end coupled to the first tubular member and a second end coupled to the second tubular member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified perspective view of the human rotator cuff and associated anatomical structure;

FIG. 2 is a schematic depiction of a full thickness tear in the supraspinatus tendon of the rotator cuff of FIG. 1;

FIG. 3 is a stylized anterior view of a patient with a shoulder of patient being shown in cross-section for purposes of illustration;

FIG. 4 is a stylized anterior view of a shoulder including a humerus and a scapula. The head of the humerus is shown mating with the glenoid fossa of the scapula at a glenohumeral joint and a sheet-like material is fixed to the tendon;

FIG. 5 is a stylized perspective view illustrating an exemplary procedure for treating a shoulder of a patient;

FIG. 6 is a stylized perspective view of a shoulder including a supraspinatus having a distal tendon with a sheet-like material fixed thereto. A proximal end of the supraspinatus is fixed to the scapula and the distal tendon of the supraspinatus is fixed to the humerus;

FIG. 7A, FIG. 7B, and FIG. 7C are multiple plan views illustrating an exemplary staple in accordance with the present detailed description;

FIG. 8 is a perspective view further illustrating the staple shown in the previous Figure;

FIG. 9 is a perspective view showing a staple push rod that may be used in conjunction with the staple shown in the previous Figure;

FIG. 10A and FIG. 10B illustrate multiple plan views of an exemplary fixation tool in accordance with the present detailed description;

FIG. 11A is a further enlarged partial cross-sectional view of a distal portion of the fixation tool shaft shown in the previous Figure;

FIG. 11B is an additional partial cross-sectional view showing a staple carried by a staple push rod and a fixation tool shaft disposed about the staple push rod;

FIG. 12A through FIG. 12C are a sequence of plan views illustrating an exemplary method and apparatus in accordance with the present detailed description;

FIG. 13A, FIG. 13B, FIG. 13C and FIG. 13D are multiview projections illustrating a fixation tool shaft shown in the previous figures;

FIG. 14 is an enlarged axial view of the fixation tool shaft shown in the previous Figure;

FIG. 15 is an additional enlarged axial view of the fixation tool shaft shown in the previous Figure;

FIG. 16 is an exploded isometric view of an exemplary fixation tool in accordance with the detailed description;

FIG. 17 is a perspective view showing an illustrative fixation tool assembly with overlying shaft removed in accordance with this detailed description;

FIG. 18A and FIG. 18B are plan views further illustrating the operation of the fixation tool assembly shown in the previous figure also with overlying shaft removed;

FIG. 19 is a perspective view showing an illustrative fixation tool assembly in accordance with this detailed description with overlying shaft removed; and;

FIG. 20A and FIG. 20B are plan views further illustrating the operation of the fixation tool assembly shown in the previous figure also with overlying shaft removed.

DETAILED DESCRIPTION

The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention.

As used herein, the term “tissue” refers to soft tissue, such as a tendon, and/or bone tissue, depending on the context in which it is used.

FIG. 3 is a stylized anterior view of a patient 20. For purposes of illustration, a shoulder 22 of patient 20 is shown in cross-section in FIG. 3. Shoulder 22 includes a humerus 14 and a scapula 12. In FIG. 3, a head 24 of humerus 14 can be seen mating with a glenoid fossa of scapula 12 at a glenohumeral joint. With reference to FIG. 3, it will be appreciated that the glenoid fossa comprises a shallow depression in scapula 12. The movement of humerus 14 relative to scapula 12 is controlled by a number of muscles including: the deltoid, the supraspinatus, the infraspinatus, the subscapularis, and the teres minor. For purposes of illustration, only the supraspinatus 26 is shown in FIG. 3.

With reference to FIG. 3, it will be appreciated that a distal tendon 28 of the supraspinatus 26 meets humerus 14 at an insertion point. Scapula 12 of shoulder 22 includes an acromium 32. In FIG. 3, a subacromial bursa 34 is shown extending between acromium 32 of scapula 12 and head 24 of humerus 14. In FIG. 3, subacromial bursa 34 is shown overlaying supraspinatus 26. Subacromial bursa 34 is one of the hundreds of bursae found the human body. Each bursa comprises a fluid filled sac. The presence of these bursae in the body reduces friction between bodily tissues. Injury and/or infection of the bursa can cause it to become inflamed. This condition is sometimes referred to as bursitis.

The exemplary methods and apparatus described herein may be used to fix tendon repair implants to various target tissues. For example, a tendon repair implant may be fixed to one or more tendons associated with an articulating joint, such as the glenohumeral joint. The tendons to be treated may be tom, partially tom, have internal micro-tears, be untom, and/or be thinned due to age, injury or overuse. Applicants believe that the methods and apparatus of the present application and related devices may provide very beneficial therapeutic effect on a patient experiencing joint pain believed to be caused by partial thickness tears and/or internal microtears. By applying a tendon repair implant early before a full tear or other injury develops, the implant may cause the tendon to thicken and/or at least partially repair itself, thereby avoiding more extensive joint damage, pain, and the need for more extensive joint repair surgery.

FIG. 4 is a stylized anterior view of a shoulder 22 including a humerus 14 and a scapula 12. In FIG. 4, a head 24 of humerus 14 is shown mating with a glenoid fossa of scapula 12 at a glenohumeral joint. A supraspinatus 26 is also shown in FIG. 4. This muscle (along with others) control the movement of humerus 14 relative to scapula 12. A distal tendon 28 of supraspinatus 26 meets humerus 14 at an insertion point 30.

In the embodiment of FIG. 4, distal tendon 28 includes a first damaged portion 36. A number of loose tendon fibers 40 in first damaged portion 36 are visible in FIG. 4. First damaged portion 36 includes a first tear 42 extending partially through distal tendon 28. First tear 42 may therefore be referred to as a partial thickness tear. With reference to FIG. 4, it will be appreciated that first tear 42 begins on the side of distal tendon 28 facing the subacromial bursa (shown in the previous Figure) and ends midway through distal tendon 28. Accordingly, first tear 42 may be referred to as a bursal side tear.

With reference to FIG. 4, it will be appreciated that distal tendon 28 includes a second damaged portion 38 located near insertion point 30. In the embodiment of FIG. 4, second damaged portion 38 of distal tendon 28 has become frayed and a number of loose tendon fibers 40 are visible in FIG. 4. Second damaged portion 38 of distal tendon 28 includes second tear 44. With reference to FIG. 4, it will be appreciated that second tear 44 begins on the side of distal tendon 28 facing the humerus 14. Accordingly, second damaged portion 38 may be referred to as an articular side tear.

In the embodiment of FIG. 4, a sheet-like implant 50 has been placed over the bursal side of distal tendon 28. With reference to FIG. 4, it will be appreciated that sheet-like implant 50 extends over insertion point 30, first tear 42 and second tear 44. Some useful methods in accordance with this detailed description may include placing a tendon repair implant on the bursal side of a tendon regardless of whether the tears being treated are on the bursal side, articular side or within the tendon. In some cases the exact location and nature of the tears being treated may be unknown. A tendon repair implant may be applied to the bursal side of a tendon to treat shoulder pain that is most likely caused by one or more partial thickness tears in the tendon. In the embodiment of FIG. 4, sheet-like implant 50 is fixed to distal tendon 28 and to humerus 14 by a plurality of staples 100 as described herein in detail.

FIG. 5 is a stylized perspective view illustrating an exemplary procedure for treating a shoulder 22 of a patient 20. The procedure illustrated in FIG. 5 may include, for example, fixing tendon repair implants to one or more tendons of shoulder 22. The tendons treated may be tom, partially tom, have internal micro-tears, be untom, and/or be thinned due to age, injury or overuse.

Shoulder 22 of FIG. 5 has been inflated to create a cavity therein. In the exemplary embodiment of FIG. 5A, a fluid supply 52 is pumping a continuous flow of saline into the cavity. This flow of saline exits the cavity via a fluid drain 54. A camera 56 provides images from inside the cavity. The images provided by camera 56 may be viewed on a display 58.

Camera 56 may be used to visually inspect the tendons of shoulder 22 for damage. A tendon repair implant in accordance with this disclosure may be fixed to a bursal surface of the tendon regardless of whether there are visible signs of tendon damage. Applicants believe that the methods and apparatus of the present application and related devices may provide very beneficial therapeutic effect on a patient experiencing joint pain believed to be caused by internal microtears, but having no clear signs of tendon tears. By applying a tendon repair implant early before a full tear or other injury develops, the implant may cause the tendon to thicken and/or at least partially repair itself, thereby avoiding more extensive joint damage, pain, and the need for more extensive joint repair surgery.

A delivery system 60 can be seen extending from shoulder 22 in FIG. 5. Delivery system 60 comprises a sheath that is fixed to a handle. The sheath defines a lumen and a distal opening fluidly communicating with the lumen. In the embodiment of FIG. 5, the distal opening of the sheath has been placed in fluid communication with the cavity created in shoulder 22.

A tendon repair implant is at least partially disposed in the lumen defined by the sheath of delivery system 60. Delivery system 60 can be used to place the tendon repair implant inside shoulder 22. Delivery system 60 can also be used to hold the tendon repair implant against the tendon. In some embodiments, the tendon repair implant is folded into a compact configuration when inside the lumen of the sheath. When this is the case, delivery system 60 may be used to unfold the tendon repair implant into an expanded shape.

The tendon repair implant may be fixed to the tendon while it is held against the tendon by delivery system 60. Various attachment elements may be used to fix the tendon repair implant to the tendon. Examples of attachment elements that may be suitable in some applications include sutures, tissue anchors, bone anchors, and staples. In the exemplary embodiment of FIG. 5, the shaft of a fixation tool 70 is shown extending into shoulder 22. In one exemplary embodiment, fixation tool 70 is capable of fixing the tendon repair implant to the tendon with one or more staples while the tendon repair implant is held against the tendon by delivery system 60.

FIG. 6 is a stylized perspective view of a shoulder 22 including a supraspinatus 26 having a distal tendon 28. With reference to FIG. 6, it will be appreciated that a tendon repair implant 50 has been fixed to a surface of distal tendon 28. Tendon repair implant 50 may comprise, for example, various sheet-like structures without deviating from the spirit and scope of the present detailed description. In some useful embodiments, the sheet-like structure may comprise a plurality of fibers. The fibers may be interlinked with one another. When this is the case, the sheet-like structure may comprise a plurality of apertures comprising the interstitial spaces between fibers. Various processes may be used to interlink the fibers with one another. Examples of processes that may be suitable in some applications including weaving, knitting, and braiding. In some embodiment, the sheet-like structure may comprise a laminate including multiple layers of film with each layer of film defining a plurality of micro-machined or formed holes. The sheet-like structure can comprise collagen material having a porous structure such as reconstituted bovine collagen. The sheet-like structure of the tendon repair implant may also comprise a plurality of electro-spun nanofiber filaments forming a composite sheet. Additionally, the sheet-like structure may comprise a synthetic sponge material that defines a plurality of pores. The sheet-like structure may also comprise a reticulated foam material. Reticulated foam materials that may be suitable in some applications are available from Biomerix Corporation of Freemont, Calif. which identifies these materials using the trademark BIOMATERIAL™.

Various attachment elements may be used to fix tendon repair implant 50 to distal tendon 28 without deviating from the spirit and scope of this detailed description. Examples of attachment elements that may be suitable in some applications include sutures, tissue anchors, bone anchors, and staples. In the exemplary embodiment of FIG. 6, a plurality of staples 100 are fixing tendon repair implant 50 to distal tendon 28. In some exemplary methods, a plurality of staples 100 may be applied using a fixation tool. The fixation tool may then be withdrawn from the body of the patient. Distal tendon 28 meets humerus 14 at an insertion point 30. With reference to FIG. 6, it will be appreciated that sheet-like implant 50 extends over insertion point 30. Tendon repair implant may be applied to distal tendon 28, for example, using the procedure illustrated in the previous Figure.

FIG. 7A, FIG. 7B, and FIG. 7C are multiple plan views illustrating an exemplary staple 100 in accordance with the present detailed description. FIG. 7A, FIG. 7B, and FIG. 7C may be collectively referred to as FIG. 7. It is customary to refer to multi-view projections using terms such as front view, top view, and side view. In accordance with this convention, FIG. 7A may be referred to as a front view of staple 100, FIG. 7B may be referred to as a side view of staple 100, and FIG. 7C may be referred to as a bottom view of staple 100. The terms top view, side view, and bottom view are used herein as a convenient method for differentiating between the views shown in FIG. 7. It will be appreciated that the staple shown in FIG. 7 may assume various orientations without deviating from the spirit and scope of this detailed description. Accordingly, the terms top view, side view, and bottom view should not be interpreted to limit the scope of the invention recited in the attached claims. A proximal direction is illustrated with an arrow P in FIG. 7. A distal direction is illustrated with a second arrow Din FIG. 7.

Staple 100 comprises a first arm 102A, a second arm 102B, and a bridge 104 extending from the proximal end of first arm 102A to the proximal end of second arm 102B. The distal end of first arm 102A abuts the proximal end of a first fluke 106A. Similarly, the distal end of second arm 102B abuts the proximal end of a second fluke 106B. In FIG. 7, first fluke 106A and second fluke 106B are shown extending distally from first arm 102A and second arm 102B, respectively. With reference to FIG. 7, it will be appreciated that first fluke 106A has a lateral extent that is larger than a lateral extent of first arm 102A. First fluke 106A is mounted eccentrically to first arm 102A in the embodiment of FIG. 7. Second fluke 106B is mounted eccentrically to second arm 102B and second fluke 106B has a lateral extent that is larger than a lateral extent of second arm 102B. First fluke 106A includes a first proximal surface 108A projecting at an outward angle in a proximal direction away from the distal end of first arm 102A. Second fluke 106B includes a second proximal surface 108B projecting at an outward angle in a proximal direction away from the distal end of second arm 102B.

With reference to FIG. 7A, it will be appreciated that first fluke 106A includes a first point 120A and a first barb 122A. Second fluke 106B includes a second point 120B and a second barb 122B. The first barb 122A and second barb 122B each have a cleft barb with two points and a valley there between. In FIG. 7, first point 120A and second point 120B are shown generally pointing in the distal direction indicated by arrow D. Also in FIG. 7, first barb 122A and second barb 122B are shown generally pointing in the proximal direction indicated by arrow P.

With reference to FIG. 7A it will be appreciated that first fluke 106A defines a first passageway 124A and second fluke 106B defines a second passageway 124B. In the exemplary embodiment of FIG. 7, first passageway 124A extends through first fluke 106A and second passageway 124B extends through second fluke 106B. It will be appreciated, however, that first passageway 124A may extend through other portions of staple 100 in some embodiments. Similarly, second passageway 124B may extend through other portions of staple 100 in some embodiments. With reference to FIG. 7B it will be appreciated that, first passageway 124A and second passageway 124B each have a generally rectangular or square cross-sectional shape. It will be appreciated, however, that first passageway 124A and second passageway 124B may have various cross-sectional shapes without deviating from the spirit and scope of the present detailed description. Further, each passageway can extend partially through the length of each fluke rather than all the way through to provide a cavity rather than a passageway.

With reference to FIG. 7C, it will be appreciated that first barb 122A of first fluke 106A defines a first notch 126A. In the exemplary embodiment of FIG. 7, first notch 126A divides first barb 122A into a first sub-barb and a second sub-barb. Second barb 122B of second fluke 106B defines a second notch 126B. In the exemplary embodiment of FIG. 7, second notch 126B divides second barb 122B into a first sub-barb and a second sub-barb. The barbs are thus clefted to form two points for greater retention in tissue.

FIG. 8 is a perspective view showing staple 100 depicted in the previous Figure. Staple 100 comprises a first arm 102A, a second arm 102B, and a bridge 104 extending from the proximal end of first arm 102A to the proximal end of second arm 102B. The distal end of first arm 102A abuts the proximal end of a first fluke 106A.

With reference to FIG. 8 it will be appreciated that first fluke 106A defines a first passageway 124A. In the exemplary embodiment of FIG. 8, first passageway 124A has a generally rectangular or square cross-sectional shape. It will be appreciated, however, that first passageway 124A may have various cross-sectional shapes without deviating from the spirit and scope of the present detailed description.

A second fluke 106B extends distally from second arm 102B with the proximal end of second fluke 106B abutting the distal end of second arm 102B. With reference to FIG. 8, it will be appreciated that second fluke 106B has a lateral extent that is larger than a lateral extent of second arm 102B. Second fluke 106B is mounted eccentrically to second arm 102B in the embodiment of FIG. 8. Similarly, first fluke 106A is mounted eccentrically to first arm 102A and first fluke 106A has a lateral extent that is larger than a lateral extent of first arm 102A.

A proximal direction is illustrated with an arrow P in FIG. 8. A distal direction is illustrated with a second arrow D in FIG. 8. With reference to FIG. 8A, it will be appreciated that first fluke 106A of first arm 102A includes a first point 120A and a first barb 122A. Second fluke 106B includes a second point 120B and a second barb 122B. In FIG. 8, first point 120A and second point 120B are shown generally pointing in the distal direction indicated by arrow D. Also in FIG. 8, first barb 122A and second barb 122B are shown generally pointing in the proximal direction indicated by arrow P. With reference to FIG. 8, it will be appreciated that first fluke 106A includes a first proximal surface 108A projecting at an outward angle in a proximal direction away from the distal end of first arm 102A. Second fluke 106B includes a second proximal surface 108B projecting at an outward angle in a proximal direction away from the distal end of second arm 102B.

FIG. 9 is a perspective view showing a staple push rod 130 that may be used in conjunction with staple 100 shown in the previous Figure. Staple push rod 130 includes a shaft 132 and a pair of stakes 134 extending distally beyond a distal end of shaft 132. The distal direction is indicated with an arrow Din FIG. 9. Stakes 134 include a first stake 134A and a second stake 134B. First stake 134A and second stake 134B form a fork 136.

In the embodiment of FIG. 9, each stake 134 has a distal portion 138 and a proximal portion 140. In some useful embodiments, each distal portion 138 is dimensioned to extend into a passage defined by a staple. In the embodiment of FIG. 9, each proximal portion 140 has a width larger than a width of each distal portion 138 so that a shoulder of each proximal portion 140 contacts a proximal surface of the staple to apply pushing forces thereto. First stake 134A comprises a first shoulder 142A and second stake 134B comprises a second shoulder 142B. Although depicted as a shoulder to provide pushing force to the staple, other designs can be utilized. For example, any larger cross section proximal portion can provide a pushing force, such as a conical increase in profile. In the embodiment of FIG. 9, proximal portion 140 of first stake 134A and the proximal portion 140 of second stake 134B diverge from one another as they extend in distal direction D away from shaft 132. In some applications, this arrangement may cause pushing forces applied to two flukes of a staple to have a laterally outward component.

In FIG. 9, first stake 134A and second stake 134B are shown assuming a substantially unstressed state. It will be appreciated that first stake 134A and second stake 134B can be resiliently urged to assume shapes other than the shape shown in FIG. 9. For example, first stake 134A and second stake 134B may be urged together so that fork 136 can be inserted into a lumen having a diameter smaller than the distance between the distal points of first stake 134A and second stake 134B shown in FIG. 9.

FIG. 10A and FIG. 10B illustrate multiple plan views of an exemplary fixation tool 144 in accordance with the present detailed description. Fixation tool 144 incorporates staple push rod 130 and is useful in delivering staple 100. FIG. 10A and FIG. 10B may be referred to collectively as FIG. 10. It is customary to refer to multi-view projections using terms such as front view, top view, and side view. In accordance with this convention, FIG. 10A may be referred to as a top view of fixation tool 144 and FIG. 10B may be referred to as a side view of fixation tool 144. The terms top view and side view are used herein as a convenient method for differentiating between the views shown in FIG. 10. It will be appreciated that the elements shown in FIG. 10 may assume various orientations without deviating from the spirit and scope of this detailed description. Accordingly, the terms top view and side view should not be interpreted to limit the scope of the invention recited in the attached claims.

In the embodiment of FIG. 10, fixation tool 144 comprises a fixation tool shaft 146 that is attached to a handle 148. Fixation tool shaft 146 comprises a wall 150 defining a lumen 152. With reference to FIG. 10, it will be appreciated that fixation tool shaft 146 includes a first prong 154A and a second prong 154B that extend distally beyond a distal end 158 of lumen 152.

In FIG. 10, a staple 100 can be seen residing in lumen 152 of fixation tool shaft 146. For purposes of illustration, a distal portion of fixation tool shaft 146 is enlarged in FIG. 10 to better show staple 100. Staple 100 comprises a first arm 102A, a second arm 102B, and a bridge 104 extending from the proximal end of first arm 102A to the proximal end of second arm 102B. The distal end of first arm 102A abuts the proximal end of a first fluke 106A. Similarly, the distal end of second arm 102B abuts the proximal end of a second fluke 106B. In FIG. 10, first fluke 106A and second fluke 106B are shown extending distally from first arm 102A and second arm 102B, respectively.

Staple push rod 130 includes a shaft 132 and a pair of stakes 134 extending distally beyond a distal end of shaft 132. The distal direction is indicated with an arrow D in FIG. 10. Stakes 134 include a first stake 134A and a second stake 134B. In FIG. 10, a distal portion of each stake 134 extends into a passageway defined by staple 100. In the embodiment of FIG. 10, a trigger 160 is pivotably coupled to handle 148 of fixation tool 144. Trigger 160 is operatively coupled to or in contact with staple push rod 130. In operation, staple push rod 130 will be advanced and/or retracted in an axial direction when trigger 160 is pivoted relative to handle 148.

FIG. 11A is a further enlarged top view of a distal portion of fixation tool shaft 146 shown in the previous Figure. For purposes of illustration, fixation tool shaft 146 is shown in partial cross-section in FIG. 11A so that staple 100 is visible residing in lumen 152. With reference to FIG. 11A, it will be appreciated that staple 100 is disposed on a distal portion of staple push rod 130. Staple 100 comprises a first arm 102A, a second arm 102B, and a bridge 104 extending from the proximal end of first arm 102A to the proximal end of second arm 102B. The distal end of first arm 102A abuts the proximal end of a first fluke 106A. Similarly, the distal end of second arm 102B abuts the proximal end of a second fluke 106B. In FIG. 11, first fluke 106A and second fluke 106B are shown extending distally from first arm 102A and second arm 102B, respectively.

First fluke 106A and second fluke 106B define a first passageway 124A and a second passageway 124B, respectively. In FIG. 11A, distal portion 138 of first stake 134A of staple push rod 130 extends into first passageway 124A defined by first fluke 106A. A distal portion 138 of second stake 134B of staple push rod 130 extends into a second passageway 124B defined by second fluke 106B of staple 100. In FIG. 11A, a first shoulder 142A of first stake 134A is shown contacting proximal surface 108 of first fluke 106A. A second shoulder 142B of second stake 134B is shown contacting proximal surface 108 of second fluke 106 in FIG. 11A. The distal portion 138 of first stake 134A extends distally of first shoulder 142A and proximal portion 140 of first stake 134A extends proximally of first shoulder 142A. The distal portion 138 of second stake 134B extends distally of second shoulder 142B and a proximal portion 140 of second stake 134B extends proximally of second shoulder 142B.

With reference to FIG. 11A, it will be appreciated that there is a gap G between staple push rod 130 and bridge 104 of staple 100. In some applications, gap G allows staple 100 to be placed in tension without bridge 104 contacting staple push rod 130. Staple 100 may be placed in tension, for example, as staple 100 is advanced into a target tissue.

FIG. 11B is an additional top view showing a distal portion of fixation tool shaft 146, staple push rod 130, and staple 100. By comparing FIG. 11A and FIG. 11B, it will be appreciated that staple push rod 130 and staple 100 have been advanced in a distal direction D relative to fixation tool shaft 146. In FIG. 11B, staple 100 is shown extending out of lumen 152 defined by fixation tool shaft 146.

In FIG. 11B, a distal portion 138 of first stake 134A of staple push rod 130 extends into a first passageway 124A defined by first fluke 106A of staple 100. In FIG. 11B, a first shoulder 142A of first stake 134A is shown contacting proximal surface 108 of first fluke 106A. Distal portion 138 of first stake 134A extends distally of first shoulder 142A and proximal portion 140 of first stake 134A extends proximally of first shoulder 142A. In some useful embodiments, the proximal portion of first stake 134A has a first width and the distal portion of first stake 134A has a second width different from the first width. In some particularly useful embodiments, the first width is greater than the first width. The arrangement allows the proximal portion of stake to engage a proximal surface of the staple to apply pushing forces to the staple.

In FIG. 11B, a distal portion 138 of second stake 134B of staple push rod 130 extends into a second passageway 124B defined by second fluke 106B of staple 100. In FIG. 11B, a second shoulder 142B of second stake 134B is shown contacting proximal surface 108 of second fluke 106B. In the embodiment of FIG. 11B, proximal portion 140 of second stake 134B may apply pushing force to proximal surface 108 of second stake 134B. Proximal portion 140 of second stake 134B extends proximally of second shoulder 142B and distal portion 138 of second stake 134B extends distally of second shoulder 142B. In the embodiment of FIG. 11B, proximal portion 140 of second stake 134B has a width larger than the width of distal portion 138 of second stake 134B so that the shoulder 142 of second stake 134B contacts proximal surface 108 of second fluke 106B to apply pushing forces thereto.

In the embodiment of FIG. 11B, first stake 134A and second stake 134B are in a substantially unstressed state. It will be appreciated that first stake 134A and second stake 134B can be resiliently urged to assume shapes other than the shape shown in FIG. 11. For example, first stake 134A and second stake 134B may be urged together so that fork 136 of staple push rod 130 and staple 100 can be inserted into lumen 152 defined by fixation tool shaft 146.

With reference to FIG. 11B, it will be appreciated that there is a gap G between staple push rod 130 and bridge 104 of staple 100. In some applications, gap G allows staple 100 to be placed in tension without bridge 104 contacting staple push rod 130. In some applications, placing staple 100 under tension may urge first fluke 106 and second fluke 106 into orientations which lock staple 100 into a target tissue. For example, first fluke 106A and second fluke 106B may be rotated so that a barb of each fluke engages the target tissue. When this is the case, the tension on the staple may keep first fluke 106A and second fluke 106B in the rotated position. Also when this is the case, the barbs of the rotated flukes may inhibit staple pullout.

FIG. 12A through FIG. 12C are a sequence of plan views illustrating an exemplary method in accordance with the present detailed description. FIG. 12A, FIG. 12B, and FIG. 12C may be collectively referred to as FIG. 12. The exemplary method illustrated in FIG. 12 may be used, for example, to fix a tendon repair implant 50 to a target tissue T using a staple 100.

At FIG. 12A, a fixation tool 144 has been used to form a first pilot hole 162A and a second pilot hole 162B in target tissue T. In the embodiment of FIG. 12, fixation tool 144 includes a fixation tool shaft 146 comprising a wall 150 defining a lumen 152. With reference to FIG. 12, it will be appreciated that fixation tool shaft 146 includes a first prong 154A and a second prong 154B that extend distally beyond a distal end 158 of lumen 152. In the embodiment of FIG. 12A, first prong 154A and second prong 154B have been urged into tissue T to form first pilot hole 162A and second pilot hole 162B. In FIG. 12A a distally directed force F applied to fixation tool shaft 146 is illustrated using an arrow. Force F may be produced, for example, by pushing on a handle that is fixed to a proximal portion of fixation tool shaft 146. It will be appreciated that in some embodiments, such as the embodiment depicted in FIG. 6, one of the first and second pilot holes may be formed through the sheet-like implant and the target tissue, and the other pilot hole may be formed directly in the target tissue without passing through the sheet-like implant. In other words, in various embodiments staples may straddle the perimeter edge of the sheet-like implant (as shown in FIG. 6), may be applied adjacent to the perimeter, and/or be applied to a central region of the implant. In some embodiments, the staples may be used to attach the implant to soft tissue and/or to bone. In FIG. 12A, a staple 100 can be seen residing in lumen 152 of fixation tool shaft 146. For purposes of illustration, fixation tool shaft 146 is shown in partial cross-section in FIG. 12A so that staple 100 is visible residing in lumen 152. With reference to FIG. 12, it will be appreciated that staple 100 is carried by a fork 136 comprising a first stake 134A and a second stake 134B. In FIG. 12A, a distal portion of first stake 134A of staple push rod 130 extends into a first passageway defined by first fluke 106A. A distal portion of second stake 134B of staple push rod 130 extends into a second passageway defined by second fluke 106B of staple 100.

In some useful embodiments, each stake is positioned relative to a prong along an inner surface of fixation tool shaft 146 so that the stakes advance into the pilot holes when the stakes are moved in a distal direction. Staple push rod 130 is slidably disposed within lumen 152 defined by fixation tool shaft 146. Fixation tool 144 includes a mechanism that is capable of creating relative axial motion between staple push rod 130 and fixation tool shaft 146 so that staple push rod 130 slides along fixation tool shaft 146.

At FIG. 12B, relative motion has been created between staple push rod 130 and fixation tool shaft 146 while distally directed force F has been continuously applied to fixation tool shaft 146. By comparing FIG. 12B and FIG. 12A, it will be appreciated that first stake 134A and second stake 134B have been advanced in a distal direction D. With reference to FIG. 12, it will also be appreciated that first stake 134A and second stake 134B have advanced into first pilot hole 162A and second pilot hole 162B, respectively. In FIG. 12B, first fluke 106A is shown residing in first pilot hole 162. Second fluke 106B is residing in second pilot hole 162 in the embodiment of FIG. 12B.

At FIG. 12C, additional relative motion has been created between staple push rod 130 and fixation tool shaft 146 while distally directed force F has been continuously applied to fixation tool shaft 146. By comparing FIG. 12C and FIG. 12B, it will be appreciated that the relative motion between staple push rod 130 and fixation tool shaft 146 has moved fixation tool shaft 146 in a proximal direction P.

By comparing FIG. 12C and FIG. 12B, it will also be appreciated that first arm 102A of staple 100 has been bent and first fluke 106A has been rotated to a toggled position. In the exemplary embodiment of FIG. 12C, force applied to first fluke 106A by first shoulder 142A has caused first fluke 106A to rotate. With continuing reference to FIG. 12C and FIG. 12B, it will be appreciated that second arm 102B of staple 100 has been bent and second fluke 106A has been rotated to a toggled position. In the exemplary embodiment of FIG. 12C, force applied to second fluke 106 b by second shoulder 142B has caused second fluke 106B to rotate.

With reference to FIG. 12C, it will be appreciated that a first through hole 164A and a second through hole 164B have been formed in tendon repair implant 50. In the embodiment of FIG. 12, first through hole 164A and a second through hole 164B were created by urging first prong 154A and second prong 154B of fixation tool shaft 146 through tendon repair implant 50.

FIG. 13A, FIG. 13B, and FIG. 13C are multiview projections illustrating a fixation tool shaft 146 shown in the previous Figures. FIG. 13D is a cross-sectional view of fixation tool shaft 146 sectioned along cutting plane D-D illustrated in FIG. 13C. These Figures may be collectively referred to as FIG. 13. Fixation tool shaft 146 of FIG. 13 comprises a wall 150 defining a lumen 152. A first prong 154A and a second prong 154B of fixation tool shaft 146 extend distally beyond a distal end 158 of lumen 152.

With reference to FIG. 13, it will be appreciated that fixation tool shaft 146 comprises a proximal portion 170, a distal portion 168 and an intermediate portion 166 disposed between proximal portion 170 and distal portion 168. In the embodiment of FIG. 13, distal portion 168 has an axial extent DA, a major lateral extent LA and a minor lateral extent LB. With reference to FIG. 13, it will be appreciated that axial extent DA is greater than both minor lateral extent LB and major lateral extent LA.

FIG. 14 is an enlarged axial view of fixation tool shaft 146 shown in the previous Figure. With reference to FIG. 14, it will be appreciated that proximal portion 170 of fixation tool shaft 146 comprises a wall 150 having an outer surface 172. In FIG. 14, outer surface 172 is illustrated using a circle. Thus, it will be appreciated that proximal portion 170 of fixation tool shaft 146 has a generally cylindrical outer shape in the exemplary embodiment of FIG. 14. In the exemplary embodiment of FIG. 14, fixation tool shaft 146 has a generally uniform wall thickness. Accordingly, the shape of proximal portion 170 may be generally described as a cylindrical tube. The shape of distal portion 168 may be described as a cylindrical-tube that has been partially flattened. In the exemplary embodiment of FIG. 14, distal portion 168 of fixation tool shaft 146 has a major lateral extent LA and a minor lateral extent LB. With reference to FIG. 14, it will be appreciated that major lateral extent LA is greater than minor lateral extent LB.

FIG. 15 is an additional enlarged axial view of fixation tool shaft 146. With reference to FIG. 15, it will be appreciated that distal portion 168 of fixation tool shaft 146 comprises a first major side SA, a second major side SB, a first minor side SC, and a second minor side SD. In the exemplary embodiment of FIG. 15, each minor side has a first central radius RA and each major side has a second central radius RB. With reference to FIG. 15, it will be appreciated that second central radius RB is greater than first central radius RA. In the exemplary embodiment of FIG. 15, first major side SA, second major side SB, first minor side SC, and second minor side SD each have a generally convex shape. In the exemplary embodiment of FIG. 15, each minor side is generally more convex than each major side.

FIG. 16 is an exploded isometric view showing an exemplary fixation tool 144 in accordance with this detailed description. In the embodiment of FIG. 16, fixation tool 144 comprises a fixation tool shaft 146 and a handle 144. In FIG. 16, handle 148 is exploded into two pieces. A proximal portion of fixation tool shaft 146 is fixed to handle 148 when fixation tool 144 is in an assembled state. Fixation tool 144 also comprises a staple push rod 130. A distal portion of staple push rod 130 extends into a lumen 152 of fixation tool shaft 146 when fixation tool 144 is in the assembled state.

Fixation tool shaft 146 comprises a wall 150 defining a lumen 152. With reference to FIG. 16, it will be appreciated that fixation tool shaft 146 includes a first prong 154A and a second prong 154B that extend distally beyond a distal end 158 of lumen 152. In some useful embodiments, first prong 154A and second prong 154B form pilot holes in a target tissue when the distal portion of fixation tool shaft 146 is pressed against the target tissue.

A staple 100 of fixation tool 144 is carried by a fork 136 in the embodiment of FIG. 16, as with prior embodiments. A fluke of staple 100 may be advanced into each pilot hole formed by the prongs of fixation tool shaft 146. Fork 136 of fixation tool 144 comprises a first stake 134A and a second stake 134B. First stake 134A and second stake 134B are fixed to a distal end of a staple push rod 130 in the embodiment of FIG. 16.

Staple push rod 130 includes a first tubular member 182, a second tubular member 184 and a force limiting mechanism 186 operably coupled between first tubular member 182 and second tubular member 184. The proximal end of first tubular member 182 is coupled to a lever 174. Lever 174 is coupled to a trigger 160. Trigger 160 is pivotably supported by handle 148 of fixation tool 144 when fixation tool 144 is in an assembled state. Trigger 160 and lever 174 form part of an actuator assembly 176 that is capable of creating longitudinal movement of first tubular member 182 of staple push rod 130 relative to fixation tool shaft 146. In operation, first tubular member 182 of staple push rod 130 will be advanced and/or retracted in an axial direction when trigger 160 is pivoted relative to handle 148. In some cases, the motion produced by actuator assembly 176 is transferred to staple 100 carried by fork 136.

Actuator assembly 176 may be used to control the motion of first tubular member 182. In the embodiment of FIG. 16, force limiting mechanism 186 will transmit longitudinal movement between first tubular member 182 and second tubular member 184 as long as the forces applied to staple 100 by staple push rod 130 are less than a predetermined value. If the forces applied to staple 100 are equal to or greater than the predetermined value, then force limiting mechanism 186 will allow relative longitudinal motion between first tubular member 182 and second tubular member 184. In some useful embodiments, this function of force limiting mechanism 186 prevents the application of undue forces to staple 100. Once the force applied to staple 100 reaches a pre-selected threshold, further rotation of trigger 160 will result in relative motion between first tubular member 182 and second tubular member 184 and will not result in the application of additional force to staple 100. Force limiting mechanism 186 is represented by a block in FIG. 16 and may comprise various force limiting arrangements without deviating from the spirit and scope of this detailed description.

FIG. 17 is a perspective view showing an illustrative fixation tool assembly 181 in accordance with this detailed description. In the embodiment of FIG. 17, fixation tool assembly 181 comprises a staple push rod 130 and a fixation tool shaft 146. A distal portion of staple push rod 130 extends into a lumen 152 defined by fixation tool shaft 146 when fixation tool assembly 181 is in an assembled state. Staple push rod 130 includes a first tubular member 182, a second tubular member 184 and a force limiting mechanism 186 operably coupled between first tubular member 182 and second tubular member 184.

In the exemplary embodiment of FIG. 17, a distal portion of first tubular member 182 is slidingly received in a lumen defined by second tubular member 184 such that first tubular member 182 and second tubular member 184 can translate relative to each other. Second tubular member 184 defines a slot 194. First tubular member 182 carries a pin 196 that is slidingly received in slot 194 such that relative rotation between first tubular member 182 and second tubular member 184 is prevented.

An actuator assembly 176 is coupled to the proximal end of first tubular member 182. Actuator assembly 176 is capable of creating longitudinal movement of first tubular member 182 of staple push rod 130 relative to fixation tool shaft 146. In the embodiment of FIG. 17, actuator assembly 176 comprises a lever 174 and a trigger 160. Lever 174 is pivotably coupled to a proximal end of first tubular member 182. Trigger 160 engages lever 174 such that rotation of trigger 160 causes rotation of lever 174.

In operation, first tubular member 182 of staple push rod 130 will be advanced and/or retracted in a longitudinal direction when trigger 160 and lever 174 are rotated. Under certain circumstances, the longitudinal motion of first tubular member 182 is transferred to second tubular member 184 by force limiting mechanism 186. When certain conditions are met, however, force limiting mechanism 186 does not transfer the longitudinal motion of first tubular member 182 to second tubular member 184.

A staple 100 is disposed at a distal end of second tubular member 184. In the embodiment of FIG. 17, force limiting mechanism 186 will transmit the longitudinal movement of first tubular member 182 to second tubular member 184 as long as the forces applied to staple 100 by staple push rod 130 are less than a predetermined value. Accordingly, longitudinal movement of first tubular member 182 of staple push rod 130 will cause substantially equivalent longitudinal movement of second tubular member 184 as long as the forces applied to staple 100 by staple push rod 130 are less than the predetermined value. If the forces applied to staple 100 are equal to or greater than the predetermined value, then force limiting mechanism 186 will allow relative longitudinal motion between first tubular member 182 and second tubular member 184. In some useful embodiments, this function of force limiting mechanism 186 prevents the application of undue forces to staple 100. Once the maximum desired force is applied to staple 100, further rotation of trigger 160 will result in relative motion between first tubular member 182 and second tubular member 184 and will not result in the application of additional force to staple 100.

In the embodiment of FIG. 17, force limiting mechanism 186 comprises a spring 188. A first end of spring 188 is pivotably coupled to first tubular member 182 at a first joint 190A. A second end of spring 188 is pivotably coupled to second tubular 184 member at a second joint 190B. In some particularly useful embodiments, spring 188 comprises a constant force spring. Spring 188 may comprise various constant force springs without deviating form the spirit and scope of the present invention. One constant force spring that may be suitable in some applications is disclosed in U.S. Pat. No. 2,630,316. With reference to FIG. 17 it will be appreciated that spring 188 comprises a plurality of wire turns arranged to extend along a longitudinal axis 198. With reference of to FIG. 17, it will be appreciated that the wire turns of spring 188 are arranged so that spring 188 extends along a straight longitudinal axis in the illustrated embodiment. Spring 188 will maintain the straight shape shown in FIG. 17 as long as the forces applied to staple 100 by staple push rod 130 are less than a predetermined value. In operation, spring 188 will transmit the longitudinal movement of first tubular member 182 to second tubular member 184 as long as the forces applied to staple 100 by staple push rod 130 are less than the predetermined value. If the forces applied to staple 100 are equal to or greater than the predetermined value, then spring 188 will bend such that the wire turns of spring 188 extend along a curvilinear longitudinal axis. When spring 188 bends, spring 188 allows relative longitudinal motion between first tubular member 182 and second tubular member 184.

With reference to FIG. 17, it will be appreciated that staple 100 is carried by a pair of stakes 134 that extend distally beyond a distal end of second tubular member 184. The distal direction is indicated with an arrow D in FIG. 17. Stakes 134 include a first stake 134A and a second stake 134B. In FIG. 17, a distal portion of each stake 134 extends into a passageway defined by staple 100. Staple 100 comprises a first arm, a second arm, and a bridge 104 extending from the proximal end of the first arm to the proximal end of the second arm. The distal end of the first arm abuts the proximal end of a first fluke 106A of staple 100. Similarly, the distal end of the second arm abuts the proximal end of a second fluke 106B.

In the embodiment of FIG. 17, a distal portion of first stake 134A extends into a first passageway defined by first fluke 106A. Similarly, a distal portion of second stake 134B extends into a second passageway defined by second fluke 106B of staple 100. A first shoulder of first stake 134A contacts a proximal surface of first fluke 106A in the embodiment of FIG. 17. A second shoulder of second stake 134B contacts a proximal surface of second fluke 106B.

Fixation tool shaft 146 of FIG. 17 comprises a wall 150 defining a lumen 152. With reference to FIG. 17, it will be appreciated that fixation tool shaft 146 includes a first prong 154A and a second prong 154B that extend distally beyond a distal end 158 of lumen 152. In some useful embodiments, first prong 154A and second prong 154B form pilot holes in a target tissue when the distal portion of fixation tool shaft 146 is pressed against the target tissue. A fluke of staple 100 may be advanced into each pilot hole formed by the prongs of fixation tool shaft 146.

FIG. 18A and FIG. 18B are plan views further illustrating the operation of fixation tool assembly 181 shown in the previous figure. FIG. 18A and FIG. 18B may be collectively referred to as FIG. 18. Fixation tool assembly 181 comprises a staple push rod 130 including a first tubular member 182, a second tubular member 184 and a force limiting mechanism 186 operably coupled between first tubular member 182 and second tubular member 184. In the exemplary embodiment of FIG. 18, a distal portion of first tubular member 182 is slidingly received in a lumen defined by second tubular member 184 such that first tubular member 182 and second tubular member 184 can translate relative to each other.

An actuator assembly 176 including a lever 174 is coupled to the proximal end of first tubular member 182. Actuator assembly 176 is capable of creating longitudinal movement of first tubular member 182 of staple push rod 130. In operation, first tubular member 182 of staple push rod 130 will be advanced and/or retracted in a longitudinal direction when lever 174 of actuator assembly 176 is rotated. Under certain circumstances, the longitudinal motion of first tubular member 182 is transferred to second tubular member 184 by force limiting mechanism 186. When certain conditions are met, however, force limiting mechanism 186 does not transfer the longitudinal motion of first tubular member 182 to second tubular member 184.

A staple 100 is disposed at a distal end of second tubular member 184. In the embodiment of FIG. 18, force limiting mechanism 186 will transmit the longitudinal movement of first tubular member 182 to second tubular member 184 as long as the forces applied to staple 100 by staple push rod 130 are less than a predetermined value. Accordingly, longitudinal movement of first tubular member 182 of staple push rod 130 will cause substantially equivalent longitudinal movement of second tubular member 184 as long as the forces applied to staple 100 by staple push rod 130 are less than the predetermined value. If the forces applied to staple 100 are equal to or greater than the predetermined value, then force limiting mechanism 186 will allow relative longitudinal motion between first tubular member 182 and second tubular member 184. In some useful embodiments, this function of force limiting mechanism 186 prevents the application of undue forces to staple 100. Once the maximum desired force is applied to staple 100, further rotation of lever 174 will result in relative motion between first tubular member 182 and second tubular member 184 and will not result in the application of additional force to staple 100.

In the embodiment of FIG. 18, force limiting mechanism 186 comprises a spring 188. A first end of spring 188 is pivotably coupled to first tubular member 182 at a first joint 190A. A second end of spring 188 is pivotably coupled to second tubular 184 member at a second joint 190B. In some particularly useful embodiments, spring 188 comprises a constant force spring. Spring 188 may comprise various constant force springs without deviating form the spirit and scope of the present invention. One constant force spring that may be suitable in some applications is disclosed in U.S. Pat. No. 2,630,316. With reference to FIG. 18 is will be appreciated that spring 188 comprises a plurality of wire turns arranged to extend along a longitudinal axis 198.

In the embodiment of FIG. 18A, the wire turns of spring 188 are arranged so that spring 188 extends along a straight longitudinal axis. Spring 188 will maintain the straight shape shown in FIG. 18A as long as the forces applied to staple 100 by staple push rod 130 are less than a predetermined value. In operation, spring 188 will transmit the longitudinal movement of first tubular member 182 to second tubular member 184 as long as the forces applied to staple 100 by staple push rod 130 are less than a predetermined value.

In the embodiment of FIG. 18B, spring 188 is bent so that the wire turns of spring 188 are arranged with spring 188 extending along a curvilinear longitudinal axis. If the forces applied to staple 100 are equal to or greater than the predetermined value, then spring 188 will bend such that the wire turns of spring 188 extend along a curvilinear longitudinal axis. The resistance to additional bending offered by spring 300 remains substantially constant as spring 300 is bent from the shape shown in FIG. 18A to the shape shown in FIG. 18B. When spring 188 bends, spring 188 allows relative longitudinal motion between first tubular member 182 and second tubular member 184. Dimension lines are used to illustrate an overall length LA and an overall length LB in FIG. 18A and FIG. 18B, respectively. With reference to FIG. 18, it will be appreciated that overall length LB is shorter than overall length LA. In the embodiment of FIG. 18, the difference between overall length LB and overall length LA is due to relative longitudinal motion between first tubular member 182 and second tubular member 184.

FIG. 19 is a perspective view showing an illustrative fixation tool assembly 180 in accordance with this detailed description. In the embodiment of FIG. 19, fixation tool assembly 180 comprises a staple push rod 130 and a fixation tool shaft 146. A distal portion of staple push rod 130 extends into a lumen 152 defined by fixation tool shaft 146 when fixation tool assembly is in an assembled state. Staple push rod 130 includes a first tubular member 182, a second tubular member 184 and a force limiting mechanism 186 operably coupled between first tubular member 182 and second tubular member 184. A staple 100 is disposed at the distal end of second tubular member 184 and a lever 174 is connected to the proximal end of first tubular member 182.

Staple 100 is carried by a fork 136 that extends distally beyond the distal end of second tubular member 184. The distal direction is indicated with an arrow D in FIG. 19. Fork 136 includes a first stake 134A and a second stake 134B. In FIG. 19, a distal portion of each stake extends into a passageway defined by staple 100. Staple 100 comprises a first arm, a second arm, and a bridge 104 extending from the proximal end of the first arm to the proximal end of the second arm. The distal end of the first arm abuts the proximal end of a first fluke 106A of staple 100. Similarly, the distal end of the second arm abuts the proximal end of a second fluke 106B.

In the embodiment of FIG. 19, a distal portion of first stake 134A extends into a first passageway defined by first fluke 106A. Similarly, a distal portion of second stake 134B extends into a second passageway defined by second fluke 106B of staple 100. A first shoulder of first stake 134A contacts a proximal surface of first fluke 106A in the embodiment of FIG. 19. A second shoulder of second stake 134B contacts a proximal surface of second fluke 106B.

Fixation tool shaft 146 of FIG. 19 comprises a wall 150 defining a lumen 152. With reference to FIG. 19, it will be appreciated that fixation tool shaft 146 includes a first prong 154A and a second prong 154B that extend distally beyond a distal end 158 of lumen 152. In some useful embodiments, first prong 154A and second prong 154B form pilot holes in a target tissue when the distal portion of fixation tool shaft 146 is pressed against the target tissue. A fluke of staple 100 may be advanced into each pilot hole formed by the prongs of fixation tool shaft 146.

An actuator assembly 176 is operably coupled to first tubular member 182 of staple push rod 130. Actuator assembly 176 is capable of moving first tubular member 182 in a longitudinal direction relative to fixation tool shaft 146. In the embodiment of FIG. 19, actuator assembly 176 comprises a lever 174 and a trigger 160. With reference to FIG. 19, it will be appreciated that lever 174 is pivotably coupled to the proximal end of first tubular member 182. Trigger 160 engages lever 174 in such a way that rotation of trigger 160 causes rotation of lever 174. In operation, first tubular member 182 of staple push rod 130 will be advanced and/or retracted in a longitudinal direction when trigger 160 and lever 174 are rotated.

In the embodiment of FIG. 19, force limiting mechanism 186 will transmit the longitudinal movement of first tubular member 182 to second tubular member 184 as long as the forces applied to staple 100 by staple push rod 130 are less than a predetermined value. Accordingly, longitudinal movement of first tubular member 182 of staple push rod 130 will cause substantially equivalent longitudinal movement of second tubular member 184 as long as the forces applied to staple 100 by staple push rod 130 are less than the predetermined value. If the forces applied to staple 100 are equal to or greater than the predetermined value, then force limiting mechanism 186 will allow relative longitudinal motion between first tubular member 182 and second tubular member 184. In some useful embodiments, this function of force limiting mechanism 186 prevents the application of undue forces to staple 100. Once the maximum desired force is applied to staple 100, further rotation of trigger 160 will result in relative motion between first tubular member 182 and second tubular member 184 and will not result in the application of additional force to staple 100.

In the embodiment of FIG. 19, force limiting mechanism 186 comprises a spring 300. Spring 300 of FIG. 19, comprises ribbon 312 that forms a roll 314 when ribbon 312 is in an unstressed state. When fixation tool assembly 180 is in an assembled state, roll 314 is supported by a roller 316 that extends through a center opening of roll 314. Roller 316 is rotatably supported by a bracket that is fixed to second tubular member 184 when fixation tool assembly 180 is in an assembled state. Second tubular member 184 defines a slot 194. First tubular member 182 carries a pin 196 that extends through slot 194. When fixation tool assembly 180 is in an assembled state, free end 318 of spring 300 is affixed to pin 196. In the embodiment of FIG. 19, the arrangement of pin 196 extending through slot 194 prevents relative rotation between first tubular member 182 and second tubular member 184.

When spring 300 is in an unstressed state, ribbon 312 forms a roll 314 as illustrated in FIG. 19. Spring 300 will maintain the rolled shape shown in FIG. 19 as long as the forces applied to staple 100 by staple push rod 130 are less than a predetermined value. In operation, spring 300 will transmit the longitudinal movement of first tubular member 182 to second tubular member 184 as long as the forces applied to staple 100 by staple push rod 130 are less than a predetermined value. If the forces applied to staple 100 are equal to or greater than the predetermined value, then spring 300 will unroll. When spring 300 unrolls, spring 300 allows relative longitudinal motion between first tubular member 182 and second tubular member 184. As ribbon 312 of roll 314 is unrolled, the force produced by spring 300 comes primarily from the portion of ribbon 312 near roll 314. Because the geometry of that region remains nearly constant as ribbon 312 unrolls, the resulting force is nearly constant.

FIG. 20A and FIG. 20B are plan views further illustrating the operation of fixation tool assembly 180 shown in the previous figure. FIG. 20A and FIG. 20B may be collectively referred to as FIG. 20. Fixation tool assembly 180 comprises a staple push rod 130 including a first tubular member 182, a second tubular member 184 and a force limiting mechanism 186 operably coupled between first tubular member 182 and second tubular member 184. In the exemplary embodiment of FIG. 20, a distal portion of first tubular member 182 is slidingly received in a lumen defined by second tubular member 184 such that first tubular member 182 and second tubular member 184 can translate relative to each other.

An actuator assembly 176 including a lever 174 is coupled to the proximal end of first tubular member 182. Actuator assembly 176 is capable of creating longitudinal movement of first tubular member 182 of staple push rod 130 relative to fixation tool shaft 146. In operation, first tubular member 182 of staple push rod 130 will be advanced and/or retracted in a longitudinal direction when lever 174 of actuator assembly 176 is rotated. Under certain circumstances, the longitudinal motion of first tubular member 182 is transferred to second tubular member 184 by force limiting mechanism 186. When certain conditions are met, however, force limiting mechanism 186 does not transfer the longitudinal motion of first tubular member 182 to second tubular member 184.

A staple 100 is disposed at a distal end of second tubular member 184. In the embodiment of FIG. 20, force limiting mechanism 186 will transmit the longitudinal movement of first tubular member 182 to second tubular member 184 as long as the forces applied to staple 100 by staple push rod 130 are less than a predetermined value.

Accordingly, longitudinal movement of first tubular member 182 of staple push rod 130 will cause substantially equivalent longitudinal movement of second tubular member 184 as long as the forces applied to staple 100 by staple push rod 130 are less than the predetermined value. If the forces applied to staple 100 are equal to or greater than the predetermined value, then force limiting mechanism 186 will allow relative longitudinal motion between first tubular member 182 and second tubular member 184. In some useful embodiments, this function of force limiting mechanism 186 prevents the application of undue forces to staple 100. Once the maximum desired force is applied to staple 100, further rotation of lever 174 will result in relative motion between first tubular member 182 and second tubular member 184 and will not result in the application of additional force to staple 100.

In the embodiment of FIG. 20, force limiting mechanism 186 comprises a spring 300. Spring 300 of FIG. 20, comprises ribbon 312 that forms a roll 314 when ribbon 312 is in an unstressed state. When fixation tool assembly 180 is in an assembled state, roll 314 is supported by a roller 316 that extends through a center opening of roll 314. Roller 316 is rotatably supported by a bracket that is fixed to second tubular member 184. First tubular member 182 carries a pin 196 that extends through a slot defined by second tubular member 184. Free end 318 of spring 300 is affixed to pin 196 in the embodiment of FIG. 20.

When spring 300 is in an unstressed state, ribbon 312 forms a roll 314 as illustrated in FIG. 20A. Spring 300 will maintain the rolled shape shown in FIG. 20A as long as the forces applied to staple 100 by staple push rod 130 are less than a predetermined value. In operation, spring 300 will transmit the longitudinal movement of first tubular member 182 to second tubular member 184 as long as the forces applied to staple 100 by staple push rod 130 are less than a predetermined value. If the forces applied to staple 100 are equal to or greater than the predetermined value, then spring 300 will umoll. When spring 300 umolls, spring 300 allows relative longitudinal motion between first tubular member 182 and second tubular member 184. In the embodiment of FIG. 20B, spring 300 has been partially umolled relative to the unstressed state of spring 300. Dimension lines are used to illustrate an overall length LA and an overall length LB in FIG. 20A and FIG. 20B, respectively. With reference to FIG. 20, it will be appreciated that overall length LB is shorter than overall length LA. In the embodiment of FIG. 20, the difference between overall length LB and overall length LA is due to relative longitudinal motion between first tubular member 182 and second tubular member 184. As ribbon 312 of roll 314 is unrolled, the force produced by spring 300 comes primarily from the portion of ribbon 312 near roll 314. Because the geometry of that region remains nearly constant as ribbon 312 unrolls, the resulting force is nearly constant.

While exemplary embodiments of the present invention have been shown and described, modifications may be made, and it is therefore intended in the appended claims and subsequently filed claims to cover all such changes and modifications which fall within the true spirit and scope of the invention. 

What is claimed is:
 1. A device for attaching a sheet-like implant to a target tissue, comprising: a sheath having a proximal end and a distal end; a fastener push rod disposed at least partially within the sheath, the fastener push rod including a first portion and a second portion; and an actuator assembly coupled to the fastener push rod first portion and capable of applying a force to the fastener push rod first portion, wherein the fastener push rod first portion is coupled to the fastener push rod second portion such that when the force applied to the fastener push rod first portion is below a force threshold, the fastener push rod first portion translates the applied force to the fastener push rod second portion, and wherein if the force applied to the fastener push rod first portion is above the force threshold, the fastener push rod first portion and the fastener push rod second portion move relative to each other so that a force above the force threshold is not translated to the fastener push rod second portion.
 2. The device of claim 1, wherein, if the force applied to the fastener push rod first portion is above the force threshold, a force that is equal to or below the force threshold is still translated to the fastener push rod second portion.
 3. The device of claim 1, further comprising a force limiting mechanism coupling the push rod first portion to the push rod second portion.
 4. The device of claim 3, wherein the force limiting mechanism comprises a constant force spring, a first end of the constant force spring being coupled to the fastener push rod first portion, and a second end of the constant force spring being coupled to the fastener push rod second portion.
 5. The device of claim 1, wherein the first portion of the fastener push rod includes a first tubular member, the second portion of the fastener push rod includes a second tubular member, and a portion of one of the first tubular member and the second tubular member is slidingly received in a lumen defined by the other of the first tubular member and the second tubular member such that the first tubular member and the second tubular member can translate relative to each other.
 6. The device of claim 5, wherein when a force above the force threshold is applied to the push rod first portion, the push rod first portion and the push rod second portion translate relative to each other.
 7. The device of claim 5, wherein one of the first tubular member and the second tubular member defines a slot, and the other of the first tubular member and the second tubular member carries a pin that is slidingly received in the slot such that relative rotation between the first tubular member and the second tubular member is prevented.
 8. The device of claim 1, wherein the sheath comprises a plurality of prongs disposed proximate the distal end of the sheath, the prongs configured for forming pilot holes when pushed against the target tissue.
 9. A device for attaching a sheet-like implant to a target tissue, comprising: a fastener push rod including a first portion and a second portion; an actuator assembly coupled to the first portion of the fastener push rod, wherein movement of the actuator assembly translates a force to the fastener push rod first portion; and a relative motion coupling between the fastener push rod first portion and the fastener push rod second portion, wherein the relative motion coupling allows relative motion between the fastener push rod first portion and the fastener push rod second portion when a force applied to the fastener push rod first portion exceeds a predetermined amount of force.
 10. The device of claim 9, wherein the relative motion coupling restricts relative motion between the push rod first portion and the push rod second portion when a force applied to the fastener push rod first portion is equal to or less than the predetermined amount of force.
 11. The device of claim 10, wherein the relative motion coupling restricts relative motion only in one direction between the fastener push rod first portion and the fastener push rod second portion when a force applied to the fastener push rod first portion is equal to or less than the predetermined amount of force.
 12. The device of claim 9, wherein the relative motion coupling comprises a constant force spring, a first end of the constant force spring being coupled to the fastener push rod first portion, and a second end of the constant force spring being coupled to the fastener push rod second portion.
 13. The device of claim 9, wherein the first portion of the fastener push rod includes a first tubular member, the second portion of the fastener push rod includes a second tubular member, and a portion of one of the first tubular member and the second tubular member is slidingly received in a lumen defined by the other of the first tubular member and the second tubular member such that the first tubular member and the second tubular member can translate relative to each other.
 14. The device of claim 13, wherein one of the first tubular member and the second tubular member defines a slot, and the other of the first tubular member and the second tubular member carries a pin that is slidingly received in the slot such that relative rotation between the first tubular member and the second tubular member is prevented.
 15. An apparatus for delivering staples to a target tissue, the apparatus comprising: a sheath having a proximal end and a distal end; a fastener push rod disposed at least partially within the sheath and translatable relative to the sheath, the fastener push rod including a first portion and a second portion; a fastener disposed on the fastener push rod second portion; and a coupler coupling the fastener push rod first portion and the fastener push rod second portion, wherein the coupler translates forces on the fastener push rod first portion to the fastener push rod second portion when the forces are below a force threshold, and wherein the coupler does not translate forces on the fastener push rod first portion to the fastener push rod second portion when the forces are above the force threshold.
 16. The apparatus of claim 15, wherein the coupler allows relative movement between the fastener push rod first portion and the fastener push rod second portion when forces on the fastener push rod first portion exceed the force threshold.
 17. The apparatus of claim 16, wherein the coupler restricts relative movement between the fastener push rod first portion and the fastener push rod second portion when the forces on the fastener push rod first portion are equal to or less than the force threshold.
 18. The apparatus of claim 15, wherein the coupler has a first longitudinal extent when the forces on the push rod first portion are equal to or less than the force threshold and the coupler has a second, smaller longitudinal extent when the forces on the push rod first portion are greater than the force threshold.
 19. The apparatus of claim 15, wherein the coupler comprises a constant force spring, a first end of the constant force spring being coupled to the fastener push rod first portion, and a second end of the constant force spring being coupled to the fastener push rod second portion.
 20. The apparatus of claim 15, wherein the first portion of the fastener push rod includes a first tubular member, the second portion of the fastener push rod includes a second tubular member, and a portion of one of the first tubular member and the second tubular member is slidingly received in a lumen defined by the other of the first tubular member and the second tubular member such that the first tubular member and the second tubular member can translate relative to each other. 